Soli is supposedly very accurate for minute movements and is very small and low-powered allowing it to be embedded in a phone, but this kind of tech has existed for a while. The Leap Motion comes in a really small, embeddable package and works over USB and can track hand movements quite accurately. It's been around for 10 years and was recently acquired by a haptics company. It's never managed to go mainstream or find any real applications outside of niche gaming.